The subject invention relates in general to the art of electrolytic cells, especially alkali metal chlorate or hypochlorite and diaphragm-type chlor-alkali cells and, more particularly, to an expandable anode assembly for use in such cells and an apparatus for forming the same.
Although the invention could be used in many types of electrolytic cells, it will be described with reference to an embodiment particularly suited for use in commercial size electrolytic cells. In these cells, the electrodes are typically large and must be maintained planar and in uniform, closely-spaced relationship for most efficient operation. As is discussed at length in U.S. Pat. No. 3,674,676 issued July 4, 1972 to Fogelman, the efficiency of such cells is closely related to the spacing or gap between the anode and the cathode. In order to reduce the gap to the minimum possible, various constructions and assembly techniques have been developed to assure that the electrode surfaces are maintained planar and parallel. (For example, see copending U.S. patent application Ser. No. 514,143, filed Oct. 11, 1974). Moreover, various adjustable or expandable structures have permitted the anodes to be collapsed to a narrow configuration for insertion into the cell between spaced cathodes and then expanded so that the working faces or anode faces are spaced a desired distance from the cathode. Expandable anodes of this general type are shown and described in the aforementioned U.S. Pat. No. 3,674,676 which is incorporated herein by reference.
The expandable anodes are desirable for many reasons. The prior designs have, however, presented certain problems. The primary problem encountered has been difficulty in maintaining the anode surfaces parallel in all positions of movement between fully collapsed and fully expanded. Additionally, it has been difficult to maintain the anode surfaces planar. That is, the loads imparted to the anode surface forming sheets by the adjustable connecting means have tended to warp the sheets in certain positions of adjustment. Prior attempts at overcoming these problems have resulted in subdividing the individual sheets or faces into plural, independent sections or adding stiffening or reinforcing members to the sheets. Neither approach has been particularly satisfactory.